Spark Plugs - V6

This procedure covers the replacement of spark plugs on the 2016-2021 Honda Civic 1.5L Turbo engine, a 4-cylinder inline configuration requiring removal of the engine cover and ignition coils.

Warnings

Tools required

Parts

• Spark plugs (iridium) × 4 — NGK DILKAR8H8S or Honda 9807B-5617W

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery terminal to prevent accidental starter engagement
4. Have replacement spark plugs ready and verify correct part number for this application

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly at the edges and pull upward to release the retaining clips. The cover is held by push clips only on this model and does not require tools for removal. Set cover aside in a clean area.
2. 2

   Disconnect ignition coil connectors
   Locate all four ignition coils along the top of the valve cover. Press the locking tab on each electrical connector and pull straight up to disconnect. Mark or note the position if connectors are not keyed differently.
3. 3

   Remove ignition coils
   Remove the single 10mm bolt securing each ignition coil. Carefully pull each coil straight up and out of the spark plug well with a twisting motion if resistance is felt. Inspect coil boots for cracks or damage.
   ⚠Do not pry on ignition coils. Use only vertical pulling force to avoid breaking the coil or damaging the spark plug terminal.
   Torque spec

   Ignition Coil Bolt10 Nm (8 lb-ft)
4. 4

   Clean spark plug wells
   Use compressed air or a clean lint-free cloth to remove any debris, dirt, or oil from around the spark plug wells. Ensure no foreign material can fall into the cylinder when spark plugs are removed.
5. 5

   Remove old spark plugs
   Using the spark plug socket with extension, carefully loosen each spark plug approximately one full turn. If significant resistance is encountered, stop and apply penetrating oil, waiting 15 minutes. Once loosened, unscrew plugs completely by hand and remove. Inspect old plugs for abnormal wear, oil fouling, or incorrect gap.
   ⚠If a spark plug breaks during removal, do not attempt to start the engine. Remove all ceramic and metal debris before proceeding.
6. 6

   Inspect spark plug condition
   Examine the electrode end of each removed spark plug. Normal wear shows light brown/gray deposits. Black sooty deposits indicate rich fuel mixture, white/blistered electrodes indicate overheating, and oil-fouled plugs suggest internal engine issues requiring further diagnosis.
7. 7

   Gap new spark plugs
   Verify the gap on each new spark plug matches Honda specification of 0.028-0.031 inches (0.7-0.8mm) for this engine. Use gap tool to check and adjust if necessary. Pre-gapped plugs should still be verified as gaps can change during shipping.
   ℹ️Gap specification is critical for proper ignition timing and fuel efficiency on turbocharged engines. Do not skip this step.
8. 8

   Apply anti-seize to spark plug threads
   Apply a thin coat of anti-seize compound to the threads of each new spark plug, keeping compound away from the electrode end (bottom 2-3 threads only). This prevents thread galling in the aluminum cylinder head and allows for easier removal during future service.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
9. 9

   Install new spark plugs
   Carefully thread each spark plug into the cylinder head by hand, ensuring it starts straight and threads smoothly. Thread each plug in at least 3-4 full turns by hand before using a socket. Using the torque wrench and spark plug socket, tighten to 20 Nm (15 lb-ft) as specified for aluminum cylinder head.
   ⚠️Cross-threading a spark plug will destroy the cylinder head threads, requiring expensive thread repair or head replacement. Always start by hand.
   Torque spec

   Spark Plug19 Nm (14 lb-ft)
10. 10

    Reinstall ignition coils
    Apply a thin layer of dielectric grease to the inside of each ignition coil boot (optional but recommended). Push each coil firmly into its spark plug well until it seats fully on the spark plug. Install the 10mm mounting bolt for each coil and torque to 10 Nm (8 lb-ft).
    Torque spec

    Ignition Coil Bolt10 Nm (8 lb-ft)
11. 11

    Reconnect electrical connectors
    Reconnect the electrical connector to each ignition coil, pressing firmly until the locking tab clicks into place. Verify each connection is secure by gently pulling on the connector body.
12. 12

    Reinstall engine cover
    Position the engine cover over the engine, aligning the retaining clips with their mounting points. Press down firmly at each clip location until the cover snaps securely into place.
13. 13

    Reconnect battery and clear codes
    Reconnect the negative battery terminal. If a check engine light was present prior to service, it may need to be cleared using an OBD-II scanner after verifying proper operation.

Reassembly

1. Ensure all four ignition coil mounting bolts are torqued properly and electrical connectors are fully seated
2. Verify engine cover is securely clipped in place at all mounting points
3. Double-check that no tools or parts were left in the engine compartment

Verification

• Start the engine and verify it idles smoothly without misfires or rough running
• Listen for any unusual sounds that were not present before the repair
• Use an OBD-II scanner to check for misfire codes (P0300-P0304) after engine reaches operating temperature
• Test drive the vehicle under light and moderate acceleration to confirm proper performance
• Check for improved throttle response and smoother acceleration, especially under boost conditions

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